Yes, there is definitely a plural of radius, and it's called radii (pronounced ray-dee-eye). When you talk about more than one radius, you would say "radii" instead of "radiuses."
Now, I know it might seem a little strange at first to use "radii" instead of "radiuses," but believe it or not, there are actually many words in the English language that follow this same pattern. In fact, these words are all part of a special group called "irregular plurals."
An irregular plural is a plural that doesn't follow the usual rules for making a word plural. So instead of adding an "s" or "es" to the end of the word, like you would with most nouns, you have to change something else about the word to make it plural. In the case of "radius," you change the "us" at the end to "i" to make "radii."
So there you have it - the plural of "radius" is "radii." And now you can impress all your friends with your grammar knowledge!
Hope that helps!
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